The present invention generally relates to apparatus and methods for thermal storage devices and, more particularly, to apparatus and methods of thermal storage devices having independent heating and cooling circuits within the device.
Thermal storage devices are necessary because when a machine, for example a laser, generates a high load of heat over a short duration, a cooling fluid forming part of a heat exchanger adjacent the machine may not be able to absorb the heat at the same rate as the heat being generated by the heat source. Typical thermal storage devices are phase change materials (“PCM”) which absorb heat energy from their surroundings as they melt from solid to liquid state and then transmit heat energy to their surroundings as they re-solidify.
Typical prior art heat exchangers employ PCM as an intermediary thermal storage devices by having a loop of fluid operating at times in heat mode and at times in cooling mode. When the heat source, for example a laser, is on, the loop is in a heat generating mode and the transport fluid picks up heat energy from the heat source, the fluid transmits heat to an adjacent fluid as part of a heat exchanger and transmits the remaining heat energy to a PCM which stores the remaining heat energy. In this example, when the laser is off, the fluid loop is then in cooling mode and the fluid runs through the same cooling loop and then into the PCM, re-absorbing some of the heat energy from the PCM, cooling the PCM as the PCM re-solidifies.
Heat exchangers and thermal storage devices may be used on aircraft where the space, weight and other limitations dictate design choices for various parts of the system, i.e. the material usable for piping in a heat exchanger, to take one example. With the continued usage of PCM in various thermal devices in increasingly more complex systems, it is useful to configure the PCM thermal storage device to allow it to have more design options to handle the diverse requirements of such systems.
As can be seen, there is a need for an apparatus and method of heat storage that has enough design flexibility to handle the diverse requirements of the heat source and of the cooling system.